The present invention relates to a mast for telescopic drilling and to a drilling rig for oil wells provided with a telescopic mast, preferably an oil-pressure one with double pistons.
The drilling rig according to the present invention is a high-mobility and electro-hydraulic drilling rig comprising a telescopic mast and an automatic drill pipe stowing and handling system for greater efficiency and operating safety.
The mast according to the present invention is a double-piston and double-effect telescopic mast to extend or retract the mast, thus increasing or decreasing its longitudinal extension.
The great demand for energy and the increasing depletion of producing oil fields has progressively pushed the search for oil to deeper and deeper areas that get more and more challenging. This new situation leads operators to drill geological formations that are more complex and hostile.
At the same time, the need has arisen to improve health and environmental safety quality standards, also known to a skilled person as health, safety, environmental and quality (HSEQ), as well as the operating performances of drilling rigs.
From the point of view of HSEQ improvement, of a reduction of drilling times and, above all, of a reduction of non-productive times, also known to a skilled person with the acronym “NPT”, the different operators working in this field have focused their technological innovation on drilling rigs with a high degree of automation, for the purpose of optimizing the entire well drilling process.
As a person skilled in the art knows, the drilling process can be divided into three macro-step: a first preparation step, during which, for example, the drilling rig is transported; a second step, during which the drilling rig is assembled or disassembled at the drilling site, also known as rig up and rig down; and a third actual drilling step, during which operators add or remove one or more drill pipes, which are connected to one another in series and define the drilling length, wherein drilling length means, as a skilled person knows, one or more drill pipes connected to one another in series.
The market mostly requires drilling rigs that can be easily moved, namely that can be moved to different drilling sites, and that feature high performances from the point of view of the actual drilling, namely that use series of drill pipes joined to one another and inserted into the well with great drilling lengths, for example starting from 27 m. Furthermore, drilling rigs are requested to have drill pipes or series of drill pipes that can be quickly inserted and removed, also fulfilling high HSEQ standards, so as to obtain a high degree of automation.
The technical features required for the drilling, in order to reduce the trip-in time and the trip-out time of a drilling system, lead the constructors of said drilling rigs to manufacture drilling rigs that allow users to use a drill string that is as long as possible. Conventional ground rigs for deep drilling use drilling lengths, also known to a skilled person as stands, starting from 27 m. Normally, this technical feature forces constructors to manufacture drilling rigs with large dimensions.
This manufacturing feature generates a technical problem concerning the transportation of a structure with remarkable dimensions, both in terms of weight and size and in terms of ability to actually maneuver the vehicle on which the mast and the other elements of the drilling rigs are arranged.
The European patent no. EP0548900 describes a mobile drilling rig comprising a telescopic mast, which can be extended by means of a central hydraulic cylinder.
Furthermore, small and medium sized drilling rigs are known, which comprise a telescopic mast and in which, during transportation, said mast is closed and arranged horizontally, for example, on a transportation vehicle.
Drilling rigs with a telescopic mast have a mast with a longitudinal extension that, in an extended operating configuration, is significantly smaller compared to fixed masts. Normally, the longitudinal extension of these masts is directly connected to the stroke that the moving system applied can perform.
The technological limit to the extension of the stroke that can be performed by the telescopic mast—and, therefore, to its maximum longitudinal extension—is strictly connected to the limitations and to the features of the oil-pressure actuator commonly used to move to the mast to during drilling operations.
Prior art hydraulic systems for ground drilling activities, in order to speed up rig up and rig down times, reduce the height of the mast, thus leading to drawbacks in terms of drilling speed and operating safety, since series of drill pipes with a reduced drilling length (13.5 or 18 m) can be used without stopping the drilling mud pumping system to add a further length.
A prejudice of the prior art establishes that, in order to use longer series of drill pipes, one needs to increase the dimensions and the weight of the mast, so as to obtain a mast with a greater longitudinal extension, thus jeopardizing, though, rig up and rig down times and the transportation of the drilling rigs.
Another problem arising from the increase in the dimensions and, in particular, in the weight of the drilling rig and, in particular, of the mast relates to the forces acting upon the mast. As a matter of fact, structures with large dimensions produce an increase in the compression force acting upon the mast, which is transferred, through the drill floor, to the base section.
A further technological restriction establishes that the structure of the mast, which is adapted to control the movements of the carriage comprising the drilling head, must be able to counter the torsion transmitted to the drill string by the drilling head itself. Furthermore, the great length of the mast can cause a bending moment, which is generated by the lack of symmetry of the compression forces relative to the longitudinal axis of the mast.
In order to solve these technical problems and avoid damages to the structure of the mast, constructors increase the dimensions of the mast even more, so as to strengthen the structure of the mast itself. The greater sturdiness of the mast, though, worsens the technical problem concerning the increase in the mass of the drilling rig.
The increase in the overall mass and dimensions of the drilling rig leads to an increase in the costs for the installation and the removal of the drilling rig itself.
The need to have drilling rigs able to reach greater drilling lengths without loosing safety and quick handling features requires a technological improvement concerning the increase in the length of the drill pipes or drill strings to be inserted into the well, for example from 13.5 m to 27 m, which can be handled by a telescopic mast.
The increase in the length of the drill pipes or drill strings leads to an increase in the length of the mast itself and, thus, to an increase in the stroke performed by the mast moving system.
Patent applications are known, for example patent application No. U.S. Pat. No. 4,249,600, in which telescopic masts are described, which comprise more than one actuator adapted to extend and reduce the longitudinal extension of the mast.
All prior art documents, in order to increase the length of the mast so as to be able to use drill strings with a length up to 27 meters, use very complex and bulky moving systems, which reduce the rig up and rig down speed of the drilling rig, thus also jeopardizing the transportation thereof.
Furthermore, patent application Ser. No. GB2270100 discloses a moving system for a travelling block, which comprises, in an embodiment, two opposite coaxial pistons. Said travelling block moving system can be implemented only in masts with a predetermined length and not in telescopic masts. This document does not provide any technical teach that is able to suggest the use of double pistons to extend or retract the longitudinal extension of the mast.